Neuroprotective mechanisms of human umbilical cord blood stem cells to retinal ganglion cells in a partial optic nerve crush rat model

Abstract

Background Optic nerve injury lead to apoptosis of retinal ganglion cells ( RGCs ), and its mechanism of apoptosis is endoplasmic reticulum stress (ERS). So, decreasing of ERS may protect the injury of RGCs. Objective The present study was to investigate the mechanisms of endoplasmic reticulum stress(ERS) and the protective effects of human umbilical cord blood stem cells on partial optic nerve crush injury. Methods The optical nerves were crushed with a 40 g clip by holding for 60 seconds to establish the partial optical nerve injury model in the left eyes of 102 SPF SD rats,and 10 μl of mRNA and 10 μl of nerve growth factor were injected into the vitreous immediately after the establishment of the model. The morphological changes of retinal ganglion cells(RGCs) were examined under the light microscope after 3,7,14,21 and 28 days and the RGCs number was calculated. The apoptosis rates of RGCs were detected by the TUNEL technique after 3, 12,24,45,72 hours and 1 week. The expression levels of GRP78 mRNA and CHOP mRNA were detected by reverse transcription polymerase chain reation (RT-PCR). This procedure followed the Regulations for the Administration of Affair Concerning Experimental Animals by Hunan Provincial Science and Technology Committee.Results The number of RGCs was significantly decreased with the prolongation of time of optical nerve injury in the model injury group,whereas the number of RGCs in the human cord blood cells group was reduced at a slower rate( Ftime =20. 100,P =0. 007 ). At various time points after the injection of human cord blood cells, the survival of RGCs was evidently increased in comparison with the model group(P＜0. 01 ). The apoptosis rate of RGCs was considerably elevated with injury time prolongation both in the model group and human cord blood cells group,but no apoptosis was seen from 3-24 hours after operation,and only a small amount of apoptotic cells were found in the human cord blood cells group from 48 hours through 1 week than in the model group(P＜0. 01 ). In the human cord blood cells group,GRP78 mRNA level was significantly higher and the CHOP mRNA level was significantly lower than those in the injury group at identical time points(P＜0. 01 ). Conclusions In the rat optic nerve partial crush model,ERS induces the apoptosis of RGCs. Human umbilical cord blood stem cells can protect RGCs from ERS injury by inhibiting apoptosis. Key words: Human umbilical cord blood stem cell; Endoplasmic reticulum stress; GRP78; CHOP; Optic nerve/crush